Apparatus and method for acquisition of communication quality

ABSTRACT

In mobile communication systems employing the CDMA method, the communication quality is acquired from the CDMA pilot channel. A communication quality acquisition apparatus comprises a delay profile acquisition unit comprising a control unit, synchronization unit and measurement unit, in addition to a data storage unit. The communication quality is measured by the synchronization unit and the measurement unit which are alternatively controlled by the control unit. When the communication quality is acquired through the CDMA pilot channel, the data acquisition efficiency can be significantly raised.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional of co-pending patent applicationSer. No. 09/825,817, filed on Apr. 4, 2001, the content of which isincorporated herein by reference in its entirety. That applicationclaims priority under 35 U.S.C. 119 to Japanese patent applicationnumber 2000-105485 filed Apr. 6, 2000, the content of which is alsoincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention generally relates to communication qualityacquisition apparatuses and methods employed in cellular mobilecommunication systems using spread signals such as CDMA(Code DivisionMultiple Access), and more specifically, to an apparatus and a methodfor acquiring communication quality through the CDMA pilot channel inthe service area.

2. Background and Relevant Art

In the prior art communication method that divides a given band intoseveral channels and then conducts communications through such channels,the communication quality is affected by thermal noise caused by adecrease in receiving power and interference noise in the co-channel andadjacent channels caused by the reuse of spatially the co-channel andadjacent channels. Then, its communication quality is identified bymeasuring the receiving power of the channel sent from the operatingbase station. Such receiving power can be measured by extracting thesignal spectrum in each desired channel by the use of frequencyconverters and frequency selection filters and then measuring the powerprovided from each filter.

However, in the case of the CDMA method, which is regarded as the mostpromising one among the future mobile communication methods, theacquisition of communication quality in the service area should beconducted in a different way.

In the CDMA method, since the allocated band is not divided into severalchannels but shared by all the communication channels, those channelsare distinguished from each other with different codes. Therefore, inorder to receive signals in a given channel for the acquisition ofcommunication quality, the code assigned to each channel must beidentified and synchronization must be established by detecting the codeinterval. Because a number of channels are required to be measured atthe same time for the acquisition of communication quality, paralleldata processing is necessary for code synchronization. Further, sincethe CDMA method improves communication quality by using a wide band, thedelay profile, which is two-dimensional data, must be acquired for theacquisition of communication quality. Then, the CDMA method poses suchproblems that its data processing becomes very complicated whenimplementing code synchronization over a number of channels to acquirecommunication quality and that the amount of data increases along withthe acquisition of delay profile.

Delay during code synchronization causes failed data acquisition andthus lowers the code synchronization accuracy. It also leads to aproblem of extended “measurement window”, which is the time interval forthe measurement of delay profile. As a result, the amount of dataprocessing grows during measurement and the portion of meaningful datain the acquired data decreases. In addition, such an increase in thedata amount caused by the acquisition of delay profile shortens themeaning data acquisition time, thus lowering the processing efficiency.

BRIEF SUMMARY OF THE INVENTION

This invention has been made to solve the above problems and its objectis, therefore, to provide an apparatus and a method for quick andefficient acquisition of communication quality. For this purpose, theinvention realizes a quick code synchronization, through control of acode synchronization unit and a delay profile measurement unit, over anumber of channels handled in parallel by conducting measurement usingthe CDMA pilot channel in the service area where the mobilecommunication services are provided by code-spread methods like CDMA.Then the improvements of code synchronization accuracy and speed enableto efficiently detect meaningful delay profile. In addition, themeasurement window can be narrowed and the delay profile acquisitionprocess is optimized. As a result, the amount of data to be acquired isreduced so that the communication quality may be acquired efficiently.

In the first invention, a communication quality acquisition apparatusreceives the CDMA pilot channels sent from a plurality of wireless basestations through the use of spread signals different from each other andhas an acquisition means for acquiring delay profile based on the spreadsignals in the CDMA pilot channels and a storage means for storing thedelay profile acquired by the acquisition means. This configurationenables to reduce the amount of necessary data and thereby efficientlyacquire communication quality.

In the second invention, the acquisition means according to the firstinvention has a synchronization means for establishing synchronizationbased on the spread signals in the CDMA pilot channels, a measurementmeans for acquiring delay profile by reverse spreading the spreadsignals in the CDMA pilot channels and a control means for controllingthe synchronization means and measurement means. This configurationenables to conduct the synchronization detection for a plurality of CDMAchannels and their re-synchronization in parallel at a time and at ahigh efficiency.

In the third invention, the storage means according to the firstinvention attaches the information of time and location to the delayprofile acquired by the acquisition means and stores the information inthe storage means.

In the fourth invention, the control means according to the secondinvention controls the synchronization means and measurement means basedon the conditions set by the user for initial error detection check,re-synchronization of each mode, off-track check and automaticre-synchronization check, or on information set for the code to bemeasured. This configuration enables to reduce fails in data acquisitiondue to delays that occur during code synchronization. Then meaningfuldata is not missed and the necessary amount of data can be minimized.

In the fifth invention, the control means according to the secondinvention controls the measurement means based on the synchronizationpoint information acquired by the synchronization means. Thisconfiguration enables to narrow the width of the “measurement window”,which is the time interval for measurement of delay profile.

In the sixth invention, the control means according to the secondinvention controls the synchronization means based on the check resultsof initial error detection, automatic re-synchronization or off-trackacquired by the measurement means. This configuration enables to raiseaccuracy in detecting synchronization points and to know the exactlocation of meaningful delay profile.

The seventh invention is a communication quality acquisition methodcomprising: the step of receiving CDMA channels sent from a plurality ofwireless base stations through the use of spread signals different fromeach other; the acquisition step of acquiring delay profile based on thespread signals in the CDMA channels; and the storage step of storing thedelay profile acquired by the acquisition step. This method enables toreduce the amount of necessary data and acquire communication qualityefficiently.

In the eighth invention, the acquisition step according to the seventhinvention comprises: the step of establishing synchronization based onthe spread signals, in the CDMA pilot channels; the measurement step ofacquiring delay profile by reverse spreading the spread signals in theCDMA pilot channels; and the control step of controlling thesynchronization step and measurement step. This method enables toconduct synchronization detection for a plurality of CDMA channels andtheir re-synchronization in parallel at a time and at a high efficiency.

In the ninth invention, at the storage step according to the seventhinvention, the information of time and location is attached to the delayprofile acquired at the acquiring step and then stored at the storagestep. In the tenth invention, at the control step according to theseventh invention, the synchronization step and measurement step arecontrolled based on the conditions set by the user for initial errordetection check, re-synchronization of each mode, off-track check andautomatic re-synchronization check, or on information set for the codethat will be measured. This method enables to reduce the failure in dataacquisition due to delay during code synchronization. Then meaningfuldata is not missed and the necessary amount of data can be minimized.

In the eleventh invention, the control step according to the eighthinvention controls the measurement step based on the synchronizationpoint information acquired at the synchronization step. This methodenables to narrow the width of “measurement window”, which is the timeinterval for measurement of delay profile.

In the twelfth invention, the control step according to the eighthinvention controls the synchronization step based on the check resultsof initial error detection, automatic re-synchronization or off-track.This method enables to raise accuracy in detecting synchronizationpoints and to know the exact location of meaningful delay profile.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description ofembodiments thereof taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an example of the communicationquality acquisition apparatus according to the present invention;

FIG. 2 is a schematic diagram illustrating the control process in thedelay profile measurement unit shown in FIG. 1;

FIG. 3A shows a schematic diagram illustrating the reception of a CDMApilot channel sent from a specific base station;

FIG. 3B shows an example of delay profile;

FIG. 4 is a flow chart illustrating an example of the method foracquiring delay profile when the communication quality acquisitionapparatus according to the invention receives a CDMA pilot channel sentfrom a given base station;

FIG. 5 is a schematic diagram illustrating an example of thesynchronization point detection process that the synchronization unitexecutes during the initial detection process shown in FIG. 4;

FIG. 6 is a schematic diagram illustrating an example of acquiring delayprofile provided by the measurement unit according to the invention;

FIG. 7A is a schematic diagram illustrating an example of acquiringdelay profile;

FIG. 7B is a flow chart illustrating an example of how to check theinitial error detection shown in FIG. 4;

FIG. 8A is a schematic diagram illustrating an example of acquiringdelay profile;

FIG. 8B is a flow chart illustrating an example of how to check theoff-track shown in FIG. 4;

FIG. 9A is a schematic diagram illustrating an example of acquiringdelay profile;

FIG. 9B is a flow chart illustrating an example of how to check theautomatic re-synchronization shown in FIG. 4;

FIG. 10 is a diagram illustrating how to use the detection requestedcode list and detection completed code list according to the invention;

FIGS. 11A to 11D are diagrams illustrating examples of the measurementcode settings, detection requested code list and detection completedcode list according to the invention;

FIG. 12 is a diagram showing the relationship of FIGS. 12A and 12B;

FIGS. 12A and 12B are flow charts illustrating examples of thesynchronization point detection for the case where there-synchronization mode is set at the automatic re-synchronization andan example of the synchronization detection process;

FIG. 13 is a diagram showing the relationship of FIGS. 13A and 13B;

FIGS. 13A and 13B are flow charts illustrating examples of thesynchronization point detection for the case where there-synchronization mode is set at the automatic re-synchronization andan example of the re-synchronization detection process;

FIG. 14 is a diagram showing the relationship of FIGS. 14A and 14B;

FIGS. 14A and 14B are flow charts illustrating examples of thesynchronization point detection for the case where there-synchronization mode is set at the manual re-synchronization and anexample of the synchronization detection;

FIG. 15 is a diagram showing the relationship of FIGS. 15A and 15B;

FIGS. 15A and 15B are flow charts illustrating examples of thesynchronization point detection for the case where there-synchronization mode is set at the manual re-synchronization and anexample of the re-synchronization detection; and

FIGS. 16A and 16B are diagrams illustrating examples of the outputprovided halfway during measurement according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a block diagram illustrating an example of thecommunication quality acquisition apparatus according to the presentinvention. The communication quality acquisition apparatus 100 has adelay profile acquisition unit 111 and a storage unit 112. Thecommunication quality acquisition apparatus 100 receives CDMA pilotchannels sent from base stations (base station A, B, C) of differentcodes (codes A, B, C) at one time. The delay profile acquisition unit111 further comprises a synchronization unit 121, a measurement unit 122and a control unit 123. The control unit 123 controls thesynchronization unit 121 and the measurement unit 122.

FIG. 2 is a schematic diagram illustrating the control process in thedelay profile measurement unit 111 shown in FIG. 1. The control processexecuted by the control unit 123 uses measurement code settinginformation, re-synchronization mode setting conditions, off-track checkconditions, initial error detection check conditions, and automaticre-synchronization check conditions, which are all determined by theuser. Also used are synchronization point information obtained by thesynchronization unit 121, and initial error detection check results,automatic re-synchronization check results and off-track check resultsobtained by the measurement unit 122.

FIG. 3A shows a schematic diagram illustrating the reception of a CDMApilot channel sent from a specific base station. Since communicationquality is improved by using a wide band in the CDMA method, theacquisition of the delay profile is important. FIG. 3B shows an exampleof delay profile. The delay profile is the electric power level of radiowaves which are drawn along the delay time of each radio wave arrivingat a receiving point in multiplexed propagation paths. In order toacquire delay profile, it is necessary to detect the code used in theCDMA pilot channel and its repetition timing in advance and thenestablish code synchronization. Code synchronization has to beestablished for every CDMA channel that is to be measured. Further, codesynchronization must be implemented not only at the beginning ofmeasurement but also during measurement each time the measurement windowis renewed and off-track takes place.

The amount of acquired data should be minimized to prevent data growthresulting from the acquisition of the delay profile that istwo-dimensional data. The width of the measurement window must beoptimized. This can be optimized by increasing the frequency of codesynchronization and refreshing the measurement window to narrow themeasurement window. Only meaningful data of the delay profile is therebystored.

FIG. 4 shows an example of the method for acquiring the delay profilewhen the communication quality acquisition apparatus receives a CDMApilot channel sent from a specific base station. When the communicationquality acquisition apparatus starts operation, the synchronization unit121 detects the synchronization point and conducts the initialacquisition of the code used in the CDMA pilot channel (S401). Next,initial error detection check is executed to determine whether theobtained initial error detection is the right one or not by themeasurement unit 122 (S402). If it is determined as a failure by thisinitial error detection check, the initial detection will be redone. Ifit is determined as successful, the mode of re-synchronization is read(S403) to conduct different operations based on the specified mode.

If the re-synchronization mode is set at “automatic”, the measurement(S404) proceeds along with the off-track check (S405), measurementcompletion check (S406) and automatic re-synchronization check (S407).If an off-track is detected in the off-track check (S405), the operationreturns to the initial detection (S401). If an automaticre-synchronization is determined to do by the automaticre-synchronization check (S407), the current synchronization point ismaintained, data measurement and storage are implemented, while theautomatic re-synchronization (S408) is carried out to detect a newsynchronization point.

On the other hand, if the re-synchronization mode is set at “manual”,the measurement (S411) is conducted along with the manualre-synchronization order check (S412) and the measurement completioncheck (S413). The above measurement operation (S411) is continued untilan order for manual re-synchronization is issued. When a manualre-synchronization order is issued, the operation returns to the initialdetection (S401).

FIG. 5 shows an example of the synchronization point detection that thesynchronization unit executes during the initial detection (S401) shownin FIG. 4. During the synchronization point detection, the correlationbetween the received signal and the reference signal for each code isprovided by a correlation examination. However, only one correlationresult is given during each code interval because the codesynchronization has not been established. The synchronization point isidentified by, for example, the location presenting the strongestcorrelation for each code and provided to the detection completed codelist (described later) as an output given halfway in the synchronizationprocess.

FIG. 6 shows an example of acquiring delay profile by the measurementmethod. The measurement unit 122 provides the degree of correlation foreach code based on the synchronization point information indicated bythe output given halfway in the synchronization process. Now that codesynchronization has been established, correlation is given for eachportion of the partial correlation intervals. This output of correlationis digitized to meet the form suitable for data storage. Later, it willbe correlated with measurement time to form a pair of path levelcorresponding to delay time. The delay profile is thereby provided as anoutput given halfway in the measurement process.

FIG. 7B shows an example of the initial error detection check (S402)shown in FIG. 4. After the initialization of the check time (S701), thedelay profile is observed (S702) as an output given halfway in themeasurement process. If a path is detected that exceeds the initialdetection threshold during the operation of determining whether there isa path exceeding the initial detection threshold (S703), the initialerror detection is determined as successful (S704). If there is no pathdetected that exceeds the initial-detection threshold, the check time isincremented (S705), and the check time and the initial detectionprotection time are compared with each other (S706). The initial errordetection is determined as a failure (S707), if the check time is equalto or longer than the initial detection protection time, namely, only ifthe period of no path that exceeds the initial detection threshold isequal to or longer than the initial detection protection time. Note thatthe initial detection threshold and the initial detection protectiontime are parameters that the user is allowed to determine as the initialerror detection check conditions.

FIG. 8B shows an example of the off-track detection check (S405) shownin FIG. 4. After the initialization of the check time (S801), the delayprofile is observed (S802) as an output given halfway in the measurementprocess. If a path is detected that exceeds the path selection levelduring the operation of determining whether there is a path exceedingthe path selection level (S803), the check time is initialized (S804)and it is determined that an off-track did not occur (S805). If there isno path detected that exceeds the path selection level, the check timeis incremented (S806), and the check time and the off-track detectionprotection time are compared with each other (S807). It is determinedthat an off-track has occurred (S808), if the check time is equal to orlonger than the off-track protection time, in other words, if the periodof no path that exceeds the path selection level is equal to or longerthan the off-track protection time. Note that the path selection leveland the off-track protection time are parameters that are set by theuser as the off-track check conditions.

FIG. 9B shows an example of the automatic re-synchronization check(S407) shown in FIG. 4. After the initialization of the check time(S901), the delay profile is observed (S902) as an output given halfwayin the measurement process. Next, the path level weighted average delaytime is calculated (S903) and it is determined whether it exceeds thewidth of the one-side re-synchronization window or not (S904). Further,it is also determined whether the sum of the path levels exceeds theautomatic re-synchronization threshold or not (S905). If either answeris NO, the check time is initialized (S906) and it is determined thatthe automatic re-synchronization will not be conducted (S907). If bothanswers are YES, the check time is incremented (S908) and compared withthe automatic re-synchronization protection time (S909).

It is determined that the automatic re-synchronization will be carriedout (S910) if the check time is equal to or longer than the automaticre-synchronization protection time, in other words, if the pulse levelweighted average delay time exceeds the width of the one-sidere-synchronization window and the existent period of path where the sumof path levels exceeds the automatic re-synchronization threshold isequal to or longer than the automatic re-synchronization protectiontime. Note that the width of the one-side re-synchronization window, theautomatic re-synchronization threshold and the automaticre-synchronization protection time are parameters that can be set by theuser as the automatic re-synchronization check conditions.

FIG. 10 shows the method using a detection requested code list and adetection completed code list. In order to receive and handle thesignals sent from more than one base station through COMA pilot channelsin parallel at a time, the detection requested code list and thedetection completed code list are used. FIG. 10 demonstrates how thethree operations, namely, the synchronization point detection operationconducted in the synchronization unit 121, initial error detection checkoperation in the measurement unit 122 and re-synchronization checkoperation (manual, automatic, off-track) in the measurement unit 122,and the detection requested code list and detection completion code listare related with one another.

First, the detection requested code list is initialized by themeasurement code settings determined by the user. The measurement codesettings describe the numbers of the codes that will be measured, namesof the base stations as reference information and search numbers forlist scanning. The detection requested code list is the code list of thecodes that will be detected. The listed codes are referred to, fromtheir top on the list, by the synchronization unit 121 forsynchronization point detection. The code of which detection has beencompleted is removed from the detection requested code list and thentransferred to the detection completion code list. The descriptions ofthe detection completed code list are the same as those of the detectionrequested code list except that the information about synchronizationpoints is added in the completed code list.

The measurement unit 122 conducts initial error detection on the codesdescribed in the detection completed code list. If the initial errordetection is determined as a failure, the corresponding code is removedfrom the detection completed code list and then transcribed on thedetection requested code list so that the operation is returned to thesynchronization unit 121. If the initial error detection is determinedas successful, the storage operation begins in the measurement unit 122and re-synchronization check operation starts. The code for whichre-synchronization starts is removed from the detection completed codelist for re-synchronization according to the setting, either of manual,automatic or on-track. Afterward, it is transferred to the detectionrequested code list and the operation is returned to the synchronizationunit 121. If the mode of re-synchronization check is set at “automatic”,the synchronization detection must be made with the current datameasurement being continued. Thus the code is described on the detectionrequested code list, while it remains in the detection completed codelist.

FIGS. 11A to 11D show examples of the measurement code settings,detection requested code list and detection completed code list. FIG.11A shows the example of measurement code settings, where a user hasspecified eight codes with the code numbers 3, 6, 9, 55, 120, 378, 412,501. FIG. 11B shows a detection requested code list that has beeninitialized according to the measurement code settings. FIG. 11C showsthe state of a detection requested code list after the detentions ofcode 3 and code 6 have been completed. FIG. 11D shows a detectioncompleted code list. The synchronization point is detected in the orderof the search numbers described on the detection requested code list.

FIGS. 12A, 12B, 13A and 13B show examples of the synchronization pointdetection for the case where the re-synchronization mode is set at theautomatic re-synchronization. After the start of operation, the settingof re-synchronization mode is read out (S1201). If its mode isdetermined to be “automatic”, the processing flow branches to a flow ofsynchronization detection or the other flow of re-synchronizationdetection.

FIGS. 12A and 12B show examples of synchronization detection. First, themeasurement code settings are read (S1202) and the detection requestedcode list is initialized (S1203). Next, according to the list searchnumbers, the codes on the detection requested code list are referred to(S1205) and the detection request is examined (S1206). If there is adetection request code on the list, the detection is started (S1207).When the detection is completed for a code, the code number is removedfrom the detection requested code list (S1208), the code number and thesynchronization point are saved (S1209) in the record of the same searchnumber on the detection completed code list. The scanning of thedetection requested code list based on the search number is constantlycontinued during measurement (S1211, S1212). Therefore, if the codenumber is described on the detection requested code list, its detectionis conducted instantaneously. In the figures that follow, X%Y representsthe remainder given when X is divided by Y, and && represents logicalmultiplication.

FIGS. 13A and 13B show examples of the re-synchronization detectionoperation. First, the initial error detection check condition (S1301),automatic re-synchronization check condition (S1302) and off-track checkcondition (S1303) are read, and then the detection completed code listis referred to (S1305). Next, it is determined whether detection iscompleted or not (S1306), and the code of which code number andsynchronization point are described on the detection completed code listis subject to the following check.

Namely, based on the check conditions and measurement data, theautomatic re-synchronization failure/success check (S1307), initialerror detection check (S1308), off-track check (S1309) and automaticre-synchronization check (S1310) are carried out. If an initial errordetect check is carried out, the operation is returned to the detectionprocess after the issue of a measurement cancellation order (S1311),data storage cancellation (S1312), removal from the detection completedcode list (S1313), and transfer to the detection requested code list(S1314). The same operations are executed if an off-track check isconducted. When an automatic synchronization check is conducted, thecode is listed on the detection requested code list (S1317) and theoperation is returned to the detection process, while the currentsynchronization point (S1315) and data saving (S1316) are continued.

During the check of failure or success in the automaticre-synchronization check (S1307), the initial error detection check atthe new synchronization point tells whether or not a new bettersynchronization point is found under the automatic re-synchronization.If the result of automatic re-synchronization check is YES, thedetection completed code list is renewed to a new one for the newsynchronization point (S1318), the synchronization point being therebyrenewed (S1319). If all the checks have failed and the currentsynchronization point is determined as the best one, the currentsynchronization point is maintained (S1320) and data storage starts(S1321).

FIGS. 14A, 14B, 15A and 15B show examples of the synchronization pointdetection for the case where the re-synchronization mode is set at themanual re-synchronization. After the start of operation, the setting ofthe re-synchronization mode is read (S1401). If its mode is determinedto be set at “manual”, the operation branches to a flow ofsynchronization detection or the other flow of re-synchronization check.

FIGS. 14A and 14B show examples of the synchronization detectionoperation. Its flow is all the same as that for the case of theautomatic re-synchronization (FIG. 12A and 12B).

FIGS. 15A and 15B show examples of the re-synchronization check. First,the initial error detection conditions are read (S1501) and then thedetection completed code list is referred to according to the searchnumber (S1503). Next, it is determined whether the detection is over ornot (S1504). The code of which code number and synchronization point aredescribed on the detection completed code list is subject to thefollowing check. If a code on the detection completed code list isdetermined to pass the initial error detection check (S1505) or a manualre-synchronization is ordered (S1506), the measurement (S1507) and datasaving (S1508), are canceled. Then the code is removed from thedetection completed code list (S1509) and moved to the detectionrequested code list (S1510) to make the process return tosynchronization detection. Unless the code passes those checks, thecurrent synchronization point is maintained (S1511) and data saving(S1512) is continued.

FIGS. 16A and 16B show the examples of an output given halfway in themeasurement process according to the invention. FIGS. 16A and 16Bdemonstrate an output given halfway in the measurement process obtainedin parallel for each code as the result of the operations in FIGS. 10 to15A and 15B. In the examples shown in FIGS. 16A and 16B, the output isprovided along with the information of time and location. This enhancesthe effectiveness of the data acquired as delay profile.

The present invention has been described in detail with respect topreferred embodiments, and it will now be apparent from the foregoing tothose skilled in the art that changes and modifications may be madewithout departing from the invention in its broader aspect, and it isthe intention, therefore, in the apparent claims to cover all suchchanges and modifications as fall within the true spirit of theinvention.

1. A communication quality acquisition apparatus comprising: anacquisition means for receiving the CDMA pilot channels sent from aplurality of wireless base stations through the use of spread signalsdifferent from each other and acquiring delay profile based on saidspread signals in said CDMA pilot channels; and a storage means forstoring the delay profile acquired by said acquisition means, whereinsaid storage means attaches the information of time and location to thedelay profile acquired by said acquisition means and stores theinformation in said storage means.
 2. A communication qualityacquisition method comprising: the acquisition step of receiving COMAchannels sent from a plurality of wireless base stations through the useof spread signals different from each other and acquiring delay profilebased on said spread signals in said CDMA channels; and the storage stepof storing the delay profile acquired by said acquisition step, whereinat said storage step the information of time and location is attached tothe delay profile acquired at said acquiring step and then stored atsaid storage step.